To store unique object elements without sorting, the most suitable interface would be a Set.
A Set is a collection that contains no duplicate elements. It provides methods to add, remove, and check if an element is present. Additionally, it does not guarantee the order of the elements.
A List is an ordered collection that allows duplicates. A Map is a collection that maps key-value pairs, and a Vector is a synchronized version of the List interface. None of these interfaces guarantee uniqueness of elements without additional implementation.
Therefore, the option that best suits the given requirement is: